Field of the Invention
The present invention relates to an electrophotographic apparatus, a process cartridge, and an image forming method.
Description of the Related Art
An electrophotographic apparatus that employs an electrophotographic process includes an electrophotographic photosensitive member, a charging device that charges the electrophotographic photosensitive member, a developing device that supplies a toner onto the electrophotographic photosensitive member to form a toner image, and a transfer device that transfers the toner image onto a transfer material such as a paper sheet, for example. A residual toner left on the electrophotographic photosensitive member without being transferred onto the transfer material is removed by a cleaning device (cleaning blade) from the electrophotographic photosensitive member.
In recent years, from the standpoint of size reduction of electrophotographic apparatuses, environmental preservation, and effective use of resources, a cleaner-less system that does not have a cleaning device and collects a residual toner back to the developing device has been proposed.
Japanese Patent Laid-Open No. 05-210300 discloses a technique in which a peripheral speed difference is caused between a charging roller and a cylindrical photosensitive member, so that a portion to which a residual toner adheres and a portion to which a residual toner has moved and adhered due to the peripheral speed difference are uniformly charged. Japanese Patent Laid-Open No. 2005-140945 states that a developer containing a certain amount of conductive particles relative to the weight of the toner is used; and a charging roller is brought into contact with an electrophotographic photosensitive member and is driven with a peripheral speed difference relative to the photosensitive member. It also states that, as a result, high uniformity of charging is achieved and a residual toner is collected to the developing device, so that fogging is suppressed. Japanese Patent Laid-Open No. 2002-123046 discloses a technique in which an auxiliary charging device is additionally used between the transfer step and the charging step so that uniform charging is achieved.